By Jeff DannerJeff has worked in both the chemical and biotech industries and is the veteran of thousands of science debates at cocktail parties and holiday dinners across the nation. In his Common Science blog, Jeff aims to make technological and scientific concepts accessible to all.

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Between 1980 and 2010 the percentage of adults in the US who were obese more than doubled, from 15% to 33%. A number of root causes have been suggested for this “obesity epidemic”, with a lot of focus on the addition of high-fructose corn syrup, a corn-based sugar, to the food supply. I decided to look into whether these concerns were valid.

Before we delve into high-fructose corn syrup (HFCS), we need to review a little background on sugars in general. Sugars are simple carbohydrates made of carbon, hydrogen and oxygen. The graphic at the top of the page shows the formula and structure for two common sugars, glucose and fructose. Table sugar, sucrose, is a disaccharide, meaning it is the combination of two sugars, one glucose and one fructose connected by a weak chemical bond. Sugar cane and sugar beets make sucrose. Sugars are often maligned as providing “empty calories” in that they provide energy but have no vitamin or mineral content.

The US grows a phenomenal amount of corn. Every year around 73 million acres are planted in this country which produce 10 billion bushels of corn. Approximately 80 percent of this corn is used directly as animal feed while the remaining 20 percent is made into corn starch, corn syrup, ethanol, and HFCS.

Corn starch is a polymer of glucose, meaning that that it is made up of long chains of individual glucose molecules. HFCS is made from corn starch in a two-step process. First you convert corn starch to corn syrup by breaking the links in the polymer chain. Corn syrup is pure glucose but it does not generate the same sensation of sweetness on the tongue as sucrose (table sugar). In the 1970’s a process was invented that converts corn starch into HFCS which is a mixture of 55% fructose and 42% glucose. HFCS is very sweet to the taste.

In the late 1970’s HFCS began making its way into the US food supply, initially in sodas like Coke and Pepsi and then into a wide variety of prepared foods. HFCS has two distinct advantages over sucrose as a food sweetener, one based on its physical properties and one based on geopolitics. With regard to physical properties, HFCS is a liquid, making it much easier to handle that sucrose which is a power. Geopolitics has significantly impacted the economics of the choice of sweeteners. In the 1970s, US sugar producers were out competed by Central and South American sugar suppliers. The US government responded by imposing tariffs on imported sugar which kept prices high for both foreign and domestic product. At the same time the US began subsidizing corn growers which kept prices for HFCS low.

The graph below shows the US per capita consumption of total caloric sweeteners (this would not include non-caloric sweeteners like saccharine or aspartame) as well as the breakdown for sucrose and HFCS. Initially, HFCS was replacing sucrose in our food supply at about a one-to-one ratio. Then, from 1980 to 2000, the total sweetener consumption abruptly rose from 120 to 150 lbs per year per person. Note that per capita consumption of HFCS started to drop in 2000.

The next graph shows the US obesity rate along with the per capita caloric sweetener consumption from 1960 to 2010. Between 1980 and 2000, the sweetener consumption and obesity rate rose in tandem. From 2000 forward, sweetener consumption starts to drop while the obesity rate stays the same.

This graph presents us with two interesting questions.

Is the rise in obesity rate from 1980 to 2000 due to the replacement in our diets of sucrose with HFCS, or from the increase in consumption of total caloric sweeteners?

An internet search on this topic will generate at lot of hits, most of them pointing the finger at HFCS. I’m skeptical. Recall that HFCS is 55% fructose and 42% glucose. Sucrose, as soon as it reaches your stomach, is broken down into to its fructose and glucose components, a 50/50 mix. Therefore, sugars in your stomach from eating equal amounts HFCS or sucrose are basically the same. This suggests to me that the rise in obesity stems from the overall increase in caloric sweetener consumption rather than whether you ate sucrose or HFCS.

If the rise in obesity rates is related to total caloric sweetener consumption, then why haven’t obesity rates fallen between 2000 and 2010?

This is a bit puzzling, but I can conceive of two plausible explanations. First, as well all know, it is much easier to gain weight than to lose it. This axiom likely holds true to the populace at large. We are collectively consuming fewer caloric sweeteners but our weight – the obesity rate – remains stubbornly at 33%.

A second possible explanation is that the reduction in caloric sweetener consumption in the population is not occurring uniformly, but rather among the already non-obese.

I know that a column touting some nefarious conspiracy to hide the sinister health effects of high-fructose corn syrup would make for great headlines, but it turns out the same tried-and-true story remains in place. Want to be healthy? Eat a healthy diet. This is pretty much what my grandfather was trying to say in the quote above.

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